Abstract

The availability of food, and hence energy, is known to influence the abundance, habitat choice and growth of individuals. In contrast, there is a paucity of knowledge on how the interaction of energy supply and social status determines patterns of residency and movement. This study tests whether the presence of conspecifics and an individual’s social status in relation to food supply influence the fitness and movement of a drift-feeding fish (Galaxias fasciatus). Using an information-theoretic approach (AIC), our analysis indicated that the most parsimonious model of fish movement among pools was one that included food supply, social rank and fish relative growth rate. Our results indicated that subordinate fish relocated more frequently compared to dominant fish, most likely as a consequence of intra-specific competition that limited the access of these smaller fish to resources and constrained their growth. Our results suggest that energy constraints may force individuals to explore new habitats in an effort to find more energetically profitable patches. We conclude that intra-specific competition mediated through the social hierarchy amongst closely interacting individuals plays a key role in determining individual growth, residency and relocation.

Notes

Acknowledgments

Many thanks to Imelda Velasquez, Hadi Pourbagher, Francis Magbanua and Amir Hamidian for their assistance with field data collection. We thank Nicky McHugh and Kim Garrett for their support in the lab and field and also Alistair Senior, Katharina Lange and Manna Warburton for their analytical advice. We are grateful to Dr. L.A. Barmuta from the University of Tasmania and to two anonymous reviewers for their invaluable comments on the manuscript. Funding was provided by the Department of Zoology, University of Otago. All experiments comply with current New Zealand laws.